Observational estimate of climate sensitivity from changes in the rate of ocean heat uptake and comparison to CMIP5 models
Unfortunately, Springerlink wants $39.95 for the privilege of reading it, so all I can do is to provide the abstract. From his blog however, Troy does show figure 5 of the paper:
Abstract. Climate sensitivity is estimated based on 0–2,000 m ocean heat content and surface temperature observations from the second half of the 20th century and first decade of the 21st century, using a simple energy balance model and the change in the rate of ocean heat uptake to determine the radiative restoration strength over this time period. The relationship between this 30–50 year radiative restoration strength and longer term effective sensitivity is investigated using an ensemble of 32 model configurations from the Coupled Model Intercomparison Project phase 5 (CMIP5), suggesting a strong correlation between the two. The mean radiative restoration strength over this period for the CMIP5 members examined is 1.16 Wm−2K−1, compared to 2.05 Wm−2K−1from the observations. This suggests that temperature in these CMIP5 models may be too sensitive to perturbations in radiative forcing, although this depends on the actual magnitude of the anthropogenic aerosol forcing in the modern period. The potential change in the radiative restoration strength over longer timescales is also considered, resulting in a likely (67 %) range of 1.5–2.9 K for equilibrium climate sensitivity, and a 90 % confidence interval of 1.2–5.1 K.
Compared to Dr. Roy Spencer’s post about models -vs- reality…
…it looks more and more as if climate sensitivity is on the lower end of the scale, rather than the high end such as was claimed recently at RealClimate by Fasullo and Trenberth which was 4°C for a doubling of CO2.
And there’s yet ANOTHER paper arguing for lower climate sensitivity. See it here
Causes of the global warming observed from the 19th century
M.J. Ring, D. Lindner, E.F. Cross, R.E. Schlesinger
Abstract. Measurements show that the Earth’s global-average near-surface temperature has increased by about 0.8℃ since the 19th century. It is critically important to determine whether this global warming is due to natural causes, as contended by climate contrarians, or by human activities, as argued by the Intergovernmental Panel on Climate Change. This study updates our earlier calculations which showed that the observed global warming was predominantly human-caused. Two independent methods are used to analyze the temperature measurements: Singular Spectrum Analysis and Climate Model Simulation. The concurrence of the results of the two methods, each using 13 additional years of temperature measurements from 1998 through 2010, shows that it is humanity, not nature, that has increased the Earth’s global temperature since the 19th century. Humanity is also responsible for the most recent period of warming from 1976 to 2010. Internal climate variability is primarily responsible for the early 20th century warming from 1904 to 1944 and the subsequent cooling from 1944 to 1976. It is also found that the equilibrium climate sensitivity is on the low side of the range given in the IPCC Fourth Assessment Report.
From the paper:
Additionally, our estimates of climate sensitivity using our SCM and the four instrumental temperature records range from about 1.5 ̊C to 2.0 ̊C. These are on the low end of the estimates in the IPCC’s Fourth Assessment Report. So, while we find that most of the observed warming is due to human emissions of LLGHGs, future warming based on these estimations will grow more slowly compared to that under the IPCC’s “likely” range of climate sensitivity, from 2.0 ̊C to 4.5 ̊C. This makes it more likely that mitigation of human emissions will be able to hold the global temperature increase since pre-industrial time below 2 ̊C, as agreed by the Conference of the Parties of the United Nations Framework Convention on Climate Change in Cancun.
Dr. Judith Curry sums it up pretty well:
In weighing the new evidence, especially improvements in the methodology of sensitivity analysis, it is becoming increasing difficult not to downgrade the estimates of climate sensitivity.
All this blows the laughable Skeptical Science claim Climate Sensitivity Single Study Syndrome, Nic Lewis Edition out of the water. Dana should quit while he’s ahead, because his arguments aren’t convincing.
h/t to Mosher